U.S. patent application number 11/480302 was filed with the patent office on 2008-01-03 for probes with self-cleaning blunt skates for contacting conductive pads.
Invention is credited to January Kister.
Application Number | 20080001612 11/480302 |
Document ID | / |
Family ID | 38812210 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001612 |
Kind Code |
A1 |
Kister; January |
January 3, 2008 |
Probes with self-cleaning blunt skates for contacting conductive
pads
Abstract
A probe having a conductive body and a contacting tip that is
terminated by one or more blunt skates for engaging a conductive
pad of a device under test (DUT) for performing electrical testing.
The contacting tip has a certain width and the blunt skate is
narrower than the tip width. The skate is aligned along a scrub
direction and also has a certain curvature along the scrub
direction such that it may undergo both a scrub motion and a
self-cleaning rotation upon application of a contact force between
the skate and the conductive pad. While the scrub motion clears
oxide from the pad to establish electrical contact, the rotation
removes debris from the skate and thus preserves a low contact
resistance between the skate and the pad. The use of probes with
one or more blunt skates and methods of using such self-cleaning
probes are especially advantageous when testing DUTs with low-K
conductive pads or other mechanically fragile pads that tend to be
damaged by large contact force concentration.
Inventors: |
Kister; January; (Portola
Valley, CA) |
Correspondence
Address: |
LUMEN INTELLECTUAL PROPERTY SERVICES, INC.
2345 YALE STREET, SECOND FLOOR
PALO ALTO
CA
94306
US
|
Family ID: |
38812210 |
Appl. No.: |
11/480302 |
Filed: |
June 29, 2006 |
Current U.S.
Class: |
324/754.2 ;
324/756.03; 324/758.04 |
Current CPC
Class: |
G01R 1/06738 20130101;
G01R 1/06733 20130101; G01R 3/00 20130101 |
Class at
Publication: |
324/754 |
International
Class: |
G01R 31/02 20060101
G01R031/02 |
Claims
1. A probe for engaging a conductive pad, said probe comprising: a)
a conductive body; b) a contacting tip having a tip width; c) at
least one blunt skate narrower than said tip width terminating said
contacting tip, said at least one blunt skate being aligned along a
scrub direction and having a curvature along said scrub direction
for producing a self-cleaning rotation; whereby a contact force
applied between said at least one blunt skate and said conductive
pad produces a scrub motion of said at least one blunt skate along
said scrub direction and said self-cleaning rotation that removes
debris from said at least one blunt skate, thereby preserving low
contact resistance.
2. The probe of claim. 1, wherein said curvature has a variable
radius of curvature.
3. The probe of claim 2, wherein said variable radius of curvature
decreases towards the front of said at least one blunt skate.
4. The probe of claim 2, wherein said variable radius of curvature
is symmetric about a midpoint of said at least one blunt skate.
5. The probe of claim 1, wherein said at least one blunt skate has
a rounded cross-section.
6. The probe of claim 1, wherein said at least one blunt skate has
a width of less than 12 .mu.m.
7. The probe of claim 1, wherein said at least one blunt skate has
a length of less than 75 .mu.m.
8. The probe of claim 1, wherein said conductive body and said
contacting tip comprise material layers.
9. The probe of claim 8, wherein said at least one blunt skate is
formed from an extension of one of said material layers.
10. The probe of claim 9, wherein said one of said material layers
having said extension that forms said at least one blunt skate is
made of a material selected from the group consisting of rhodium
and cobalt.
11. The probe of claim 1, wherein said at least one blunt skate
comprises at least two blunt skates that are parallel.
12. The probe of claim 1, wherein said at least one blunt skate
comprises at least two blunt skates that are staggered along said
scrub direction.
13. The probe of claim 1, wherein said conductive pad is a low-K
conductive pad.
14. A method for engaging a conductive pad with a probe having a
conductive body and a contacting tip, said method comprising: a)
terminating said contacting tip with at least one blunt skate
narrower than a tip width of said contacting tip; b) providing said
at least one blunt skate with a curvature aligned along a scrub
direction for producing a self-cleaning rotation; c) applying a
contact force between said at least one blunt skate and said
conductive pad such that said at least one blunt skate undergoes a
scrub motion along said scrub direction and said self-cleaning
rotation that removes debris from said at least one blunt skate,
thereby preserving low contact resistance.
15. The method of claim 14, further comprising augmenting said
self-cleaning rotation by increasing said contact force.
16. The method of claim 15, wherein said augmenting of said
self-cleaning rotation is performed after at least two touch-down
cycles.
17. The method of claim 14, wherein a test current i is applied
after applying said contact force.
18. The method of claim 14, wherein said at least one blunt skate
comprises at least two blunt skates that are parallel.
19. The method of claim 14, wherein said at least one blunt skate
comprises at least two blunt skates that are staggered along said
scrub direction.
20. A probe card with probes for engaging a conductive pads of a
device under test, each of said probes comprising: a) a conductive
body; b) a contacting tip having a tip width; c) at least one blunt
skate narrower than said tip width terminating said contacting tip,
said at least one blunt skate being aligned along a scrub direction
and having a curvature along said scrub direction for producing a
self-cleaning rotation; whereby a contact force applied between
said at least one blunt skate and said conductive pad produces a
scrub motion of said at least one blunt skate along said scrub
direction and said self-cleaning rotation that removes debris from
said at least one blunt skate, thereby preserving low contact
resistance.
21. The probe card of claim 19, further comprising a source for
delivering a test current i to said probes.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 10/850,921 filed on May 21, 2004, U.S.
application Ser. No. 10/888,347 filed on Jul. 9, 2004 and U.S.
application Ser. No. 11/450,977 filed on Jun. 9, 2006.
FIELD OF THE INVENTION
[0002] This invention relates generally to probes for testing
devices under test (DUTs), and in particular to probes with
contacting tips terminated in blunt skates to promote self-cleaning
on contact with contacting pads as well as self-cleaning
methods.
BACKGROUND ART
[0003] The testing of semiconductor wafers and other types of
integrated circuits (ICs), collectively known as devices under test
(DUTs), needs to keep pace with technological advances. Each IC has
to be individually tested, typically before dicing, in order to
ensure that it is functioning properly. The demand for testing
products is driven by two considerations: new chip designs and
higher volumes. As chips become increasingly powerful and
complicated, the need for high-speed probe card devices to test
them becomes more and more deeply felt.
[0004] In particular, chips are getting smaller and they have more
tightly spaced conductive pads. The pads are no longer located
about the circuit perimeter, but in some designs may be found
within the area occupied by the circuit itself. As a result, the
density of leads carrying test signals to the pads is increasing.
The pads themselves are getting thinner and more susceptible to
damage during a test. Meanwhile, the need to establish reliable
electrical contact with each of the pads remains.
[0005] A well-known prior art solution to establishing reliable
electrical contact between a probe and a pad of a DUT involves the
use of probes that execute a scrub motion on the pad. The scrub
motion removes the accumulated oxide layer and any dirt or debris
that acts as an insulator and thus reduces contact resistance
between the probe and the pad. For information about corresponding
probe designs and scrub motion mechanics the reader is referred to
U.S. Pat. No. 5,436,571 to Karasawa; U.S. Pat. Nos. 5,773,987 and
6,433,571 both to Montoya; U.S. Pat. No. 5,932,323 to Throssel and
U.S. Appl. 2006/0082380 to Tanioka et al. Additional information
about the probe-oxide-semiconductor interface is found in U.S. Pat.
No. 5,767,691 to Verkuil.
[0006] In order to better control the scrub motion, it is possible
to vary the geometry of the contacting tip of the probe. For
example, the radius of curvature of the tip may be adjusted. In
fact, several different radii of curvature can be used at different
positions along the probe tip. For additional information about
probe tips with variable radii of curvature the reader is referred
to U.S. Pat. No. 6,633,176 and U.S. Appl. 2005/0189955 both to
Takemoto et al.
[0007] Although the above-discussed prior art apparatus and methods
provide a number of solutions, their applications when testing
conductive pads that are thin or prone to mechanical damage due to,
e.g., their thickness or softness is limited. For example, the
above probes and scrub methods are not effective when testing DUTs
with low-K conductive pads made of aluminum because such pads are
especially prone to damage by probes with tips that either cut
through the aluminum or introduce localized stress that causes
fractures. In fact, a prior art solution presented in U.S. Pat. No.
6,842,023 to Yoshida et al. employs contact probe whose tip tapers
to a sloping blade or chisel. The use of this type of probe causes
a knife edge and/or single point of contact effects to take place
at the tip-pad interface. These effects can causes irreversible
damage to pads, especially low-K conductive pads made of aluminum
or soft metal. On the other hand, when insufficient contact force
is applied between the probe tip and the pad, then the oxide and
any debris at the probe-pad interface will not be efficiently
removed.
[0008] The problem of establishing reliable electrical contact with
fragile conductive pads remains. It would be an advance in the art
to provide are probes that can execute effective scrubbing motion
and are self-cleaning, while at the same time they do not cause
high stress concentration in the pad. Such probes need to be
adapted to probe cards for testing densely spaced pads.
OBJECTS AND ADVANTAGES
[0009] In view of the above prior art limitations, it is an object
of the invention to provide probes that are self-cleaning upon
contact and avoid long-term accumulation of debris to thus preserve
their ability to establish good electrical contact or low contact
resistance R.sub.c.
[0010] It is a further object of the invention to provide probes
that reduce mechanical stress concentration in the pads of the DUT
being tested to render the probes suitable for testing low-K
conductive pads.
[0011] A still further object of the invention is to provide probes
and self-cleaning methods that can be applied in various probe
geometries, probe cards and test arrangements.
[0012] These and other objects and advantages of the invention will
become apparent from the ensuing description.
SUMMARY OF THE INVENTION
[0013] The objects and advantages of the invention are secured by a
probe designed for engaging a conductive pad of a device under test
(DUT). The probe has an electrically conductive body that ends in a
contacting tip of a certain tip width. At least one blunt skate
that is narrower than the tip width terminates the contacting tip.
The blunt skate is aligned along a scrub direction and also has a
certain curvature along the scrub direction to produce a
self-cleaning rotation or rocking motion. As a result of the
alignment and skate geometry, once a contact force is applied
between the blunt skate and the conductive pad the skate undergoes
a scrub motion along the scrub direction and also a self-cleaning
rotation. While the scrub motion clears oxide from the pad to
establish electrical contact, the rotation removes debris from the
skate and thus preserves low contact resistance between the skate
and the pad.
[0014] To promote the self-cleaning rotation the curvature of the
blunt skate needs to have an appropriate radius of curvature.
Preferably, the radius of curvature is variable and decreasing
towards the front of the skate. Since the skate is preferably
symmetric about a midpoint, the same variable radius of curvature
can be used in the back half of the skate. In one embodiment the
cross-section of the blunt skate is flat and in another it has a
rounded cross-section. In general, it is preferable that the skate
have a width of less than 12 .mu.m and a length of less than 75
.mu.m. It should be noted that probes with blunt skates in this
dimensional range are very well-suited for contacting DUTs with
low-K conductive pads that are mechanically fragile.
[0015] In some embodiments the probe is made of material layers.
Such layers can be grown, e.g., in a deposition process. In these
embodiments the blunt skate can be formed from an extension of one
of the material layers. The most appropriate material layer for
forming a blunt skate from its extension is a hard conductive
material such as rhodium or cobalt. In either the layered probe
embodiments or still other embodiments it is possible to provide
two or more blunt skates. The skates can be arranged parallel to
each other. Alternatively, or in addition the skates can be
staggered along the scrub direction.
[0016] The invention further extends to a method for engaging
probes that have conductive bodies and contacting tips terminating
in one or more blunt skates with a conductive pad. The skate or
skates are narrower than the tip width. The skate or skates are
provided with a curvature aligned along the scrub direction for
producing the self-cleaning rotation. The application of a contact
force between the skate and the conductive pad causes the skate to
undergo a scrub motion along the scrub direction and a
self-cleaning rotation that removes debris. The debris is usually
accumulated during previous engagements with or touch-downs on pads
and its removal from the skate preserves low contact
resistance.
[0017] In accordance with a preferred embodiment of the method, the
contact force is augmented to increase the self-cleaning rotation.
This can be done whenever excess debris accumulates. Typically this
will take place after several cycles, and thus the contact force
can be augmented after two or more touch-down cycles to augment the
self-cleaning rotation.
[0018] To perform a test, a test current i is applied to the probe
after applying the contact force. This means that the skate
delivers the test current i to the pad after performing the scrub
motion that removes any oxide from the pad and establishing
electrical contact with it. Note that no current is applied when
performing increased self-cleaning rotation of the skate. The same
method is applied when two or more parallel and/or staggered skates
are used.
[0019] The probes of invention can be used in various apparatus and
situations. For example, the probes can be used in a probe card for
testing devices under test (DUTs) such as semiconductor wafers. The
probe card requires appropriate design and devices, such as a
source for delivering the test current i as well as arrangements
for providing the overdrive to apply the contact force between the
probes and the pads of the DUT.
[0020] A detailed description of the preferred embodiments of the
invention is presented below in reference to the appended drawing
figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0021] FIG. 1 is a three-dimensional view of a portion of a probe
card employing probes with blunt skates according to the
invention.
[0022] FIG. 2A is a plan side view of a contacting tip of a single
probe from FIG. 1 equipped with a blunt skate.
[0023] FIG. 2B is a front cross-sectional view of the contacting
tip of the single probe from FIG. 1.
[0024] FIG. 3A-D are three-dimensional views of the successive
steps in engaging a blunt skate with a low-K conductive pad.
[0025] FIG. 4 (prior art) is a graph of contact resistance R.sub.c
between a typical flat contacting tip and a conductive pad as a
function of touch-down cycles.
[0026] FIG. 5 is a graph of contact resistance R.sub.c between a
contacting tip equipped with a blunt skate in accordance with the
invention and a conductive pad.
[0027] FIG. 6 is a diagram comparing the performance of a prior art
chisel tip and a tip with a blunt skate in accordance with the
invention.
[0028] FIG. 7A-D are three-dimensional views of alternative probe
tips with one or more blunt skates according to the invention.
[0029] FIG. 8A-B are microscope images of a preferred blunt skate
prior to use and after one million touch-down cycles.
DETAILLED DESCRIPTION
[0030] A portion of a probe card assembly 100 employing probes 102
according to the invention is shown in FIG. 1. Assembly 100 has a
block 104 for holding probes 102 by their contact ends 106. A space
transformer, electromechanical arrangements as well as a source for
providing a test current i to be applied to contact ends 106 are
not shown in this drawing for reasons of clarity.
[0031] Probes 102 have electrically conductive bodies 108 that end
in contacting tips 110 of a tip width 112. Bodies 108 have suitable
mechanical properties for engaging with conductive pads or bumps of
a device under test (DUT). For example, bodies 108 can be straight,
bent or have more complex geometries to ensure sufficient
mechanical strength and compliance, as will be appreciated by those
skilled in the art. In fact, although probes 102 have bodies 108
that are bent in the present embodiment, the invention can be
practiced with probes of any geometry.
[0032] Tips 110 terminate in blunt skates 114 that are narrower
than tip width 112. In fact, skate width 116 is typically a
fraction of tip width 112. For example, tip width 112 can be on the
order of 75 .mu.m while skate width 116 is about 12 .mu.m or less.
Skates 114 are aligned along a scrub direction 120 indicated by an
arrow.
[0033] As better shown in the plan side view of FIG. 2A, each blunt
skate 114 has a certain curvature along scrub direction 120. In
other words, the ridge of skate 114 that is aligned with scrub
direction 120 has a certain curvature along that direction. The
curvature is defined in such a way as to produce a self-cleaning
rotation sometimes also referred to as pivoting or rocking motion
of skate 114. In the present embodiment, the curvature has a
variable radius of curvature R that decreases toward a front 122 of
skate 114. More specifically, the radius of curvature has a small
value R.sub.m at front 122 and a larger value R.sub.n near the
center of skate 114.
[0034] Skate 114 in the present embodiment is symmetric about a
center line 124 that passes through a midpoint 126 of skate 114.
Therefore, the same variable radius of curvature is found in the
back half of skate 114. It is important that the curvature at every
point along skate 114 that will engage with a pad is sufficiently
large to avoid single point of contact or knife edge effects. These
effects cause large amounts of local stress to develop in the pad
and in the case of low-K pads can cause damage. Such effects are
especially likely to develop along skate 114 at front and back
regions, such as region 128 indicated in hatching. To further help
avoid these effects, the cross-section of skate 114 has a rounded
rather than a flat cross section, as better visualized in the front
cross-sectional view of FIG. 2B.
[0035] The operation of probes 102 will be explained in reference
to the three-dimensional views shown in FIGS. 3A-D. In FIG. 3A
contacting tip 110 with blunt skate 114 is positioned above a
conductive pad 130 of a device under test (DUT) 132. Only a portion
of DUT 132 is shown for clarity. In this position, no test current
i is applied (i=O) to probe 102.
[0036] It is understood that DUT 132 can be any device that
requires electrical testing including, for example, a semiconductor
wafer bearing integrated circuits. Also., it is understood that pad
130 can have any geometry and can also be in the form of a solder
bump or any other form suitable for establishing electrical
contact. In the present embodiment pad 130 is a low-K conductive
pad.
[0037] In FIG. 3B a contact force F.sub.c is applied between blunt
skate 114 and low-K conductive pad 130. This force can be delivered
by any suitable mechanism well-known to an artisan skilled in the
art. At this time, there is still no test current applied
(i=0).
[0038] FIG. 3C illustrates how tip 110 pivots and skate 114
performs a scrub motion along scrub direction 120. The scrub motion
is caused by a scrub force F.sub.s1 that is due to contact force
F.sub.c. The purpose of scrub motion of skate 114 is to clear oxide
from pad 130 to establish electrical contact between skate 114 and
pad 130. The alignment of skate 114 with scrub direction 120 and
the geometry of skate 114, namely its curvature causes the scrub
motion to be accompanied by a self-cleaning rotation or pivoting of
skate 114.
[0039] The self-cleaning rotation removes debris 134 that is
accumulated on skate 114 or that is originally located on pad 130
from skate 114. Typically, debris 134 accumulates on skate 114
during previous engagements with or touch-downs on pads. The
self-cleaning rotation pushes debris 134 to the back and off the
sides of skate 114. Removal of debris 134 from the skate-pad
interface enables a low contact resistance R.sub.c to be preserved
between skate 114 and pad 130. Once such low contact resistance
R.sub.c has been established, a test current i=i.sub.o is applied
to pad 130.
[0040] FIG. 3D shows the effects of augmenting contact force
F.sub.c to further increase the self-cleaning rotation of skate
114. This can be done whenever excess of debris 134 accumulates on
skate 114. In a preferred embodiment of the method of invention,
contact force F.sub.c is augmented after a certain number of
touch-down cycles or whenever the contact resistance is observed to
reach unacceptable levels. This may occur after two or more
touch-down cycles or when resuming testing after a long stand-by
period. Note that the resultant scrub force F.sub.s2 is larger as a
result of the increased contact force F.sub.c and that no test
current (i=0) is applied during this procedure.
[0041] A graph 140 in FIG. 4 shows the contact resistance R.sub.c
between a typical flat prior art contacting tip and a conductive
pad as a function of touch-down cycles. Clearly, contact resistance
R.sub.c increases from a nominal value R.sub.o of about 1 .OMEGA.
as a function of cycles n. The slope of the increase grows as a
function of n until reaching a maximum resistance R.sub.max.
Testing the pads becomes impossible once contact resistance R.sub.c
reaches R.sub.max. At this point, the prior art tips are sanded
down to remove debris and recover nominal contact resistance
R.sub.o. This corresponds to the dashed portion 142 of graph 140.
Unfortunately, sanding down accelerates the accumulation of debris
on the tip. This causes the slope of contact resistance increase to
become steeper and reach the unacceptably high value R.sub.max even
sooner. Another sanding denoted by dashed portion 144 is required
to again recover nominal resistance R.sub.o.
[0042] FIG. 5 shows an exemplary graph 150, of contact resistance
R.sub.c between contacting tip 110 with blunt skate 114 in
accordance with the invention and a conductive pad. As contact
resistance R.sub.c increases from nominal value R.sub.o, the
self-cleaning rotation of skate 114 tends to restore it to R.sub.o.
In some cases no additional intervention is necessary. If R.sub.c
does begin to grow too much and an immediate decrease of contact
resistance R.sub.c is desired, then the contact force F.sub.c is
augmented to increase the self-cleaning rotation of skate 114.
Portions 152 of graph 150 visualize the corresponding reductions of
contact resistance R.sub.c to nominal value R.sub.o.
[0043] FIG. 6 shows a comparison in the concentration of mechanical
stress caused in low-K conductive pad 130 by a prior art chisel
probe tip 160 and a blunt skate 162 with a flat cross-section in
accordance with the present invention. Pad 130 is made of aluminum
and both tip 160 and skate 162 are made of Rhodium. Chisel 160 has
a 60 degree taper angle, a 2 mil radius at its contact tip and is
60 .mu.m long. Skate 162 is 10 .mu.m wide, its ends are rounded
with a 10 mil radius of curvature and it is also 60 .mu.m long. The
contact force F.sub.c applied in each case is 8 g. The stress
caused by prior art chisel tip 160 is very large and concentrated
in the middle of pad 130. This causes mechanical failure of pad 130
by fracture. In contrast, the stress is well-distributed when blunt
skate 114 according to the invention is used to establish
electrical contact with pad 130.
[0044] Various types of probes can employ blunt skates according to
the invention, as illustrated in FIGS. 7A-D. In some embodiments a
probe 200 is made of several material layers 202, 204, 206, as
illustrated in FIG. 7A. Such layers can be grown, e.g., in a
deposition process. In these embodiments a blunt skate 208 can be
formed at a tip 210 from an extension of one of the material
layers. In the embodiment shown, it is the extension of the central
or sandwiched material layer 204 that forms skate 208. The most
appropriate material layer for forming a blunt skate from its
extension is a hard conductive material such as rhodium or cobalt.
In fact, material layer 204 is made of rhodium in the present
embodiment. In alternative probes having more layers extensions of
other than central layers can be used. In fact, even the outer-most
layers may be extended to form blunt skates according to the
invention.
[0045] FIG. 7B illustrates a probe 220 with a laser machined blunt
skate 222. For example, skate 222 has a higher aspect ratio than
previous skates and also a single radius of curvature. Such
geometry can be employed when relatively short scrub motion is
imposed by a higher pitch of conductive pads. In fact, the
curvature of skate 222 can be adjusted in concert with the
characteristics of the scrub motion as conditioned by the geometry
of the probe. These characteristics may include, among other, scrub
length, scrub depth and scrub velocity.
[0046] In either the layered probe embodiments or still other
embodiments it is possible to provide two or more blunt skates, as
illustrated by probe 230 of FIG. 7C. Probe 230 is made of three
material layers 232, 234, 236 and of those the side layers 232, 236
are extended to form blunt skates 238, 240. Skates 238, 240 are
arranged parallel to each other and along the scrub direction. Of
course, more than two skates 238, 240 can be accommodated on the
tip of a probe when more material layers are available.
[0047] Still another alternative embodiment is shown in FIG. 7D.
Probe 250 shown here has five material layers 252, 254, 256, 258
and 260 with layers 252, 256 and 260 being extended. Three blunt
skates 262, 264, 266 are formed from extensions of layers 252, 256,
260. These skates are also parallel to each other, but in addition
they are staggered along the scrub direction.
[0048] A person skilled in the art will appreciate that various
other combinations of skates are possible. In addition, the blunt
skates can be employed at the tips of various types of probes,
including probes that are linear or bent. For example, zig-zag
probes, S-shaped probes or probes with a knee can employ one or
more blunt skates each to improve contact resistance with the pads
of the DUTs. Also, when equipped with the blunt skates of the
invention, these probes can be used to contact more fragile
conductive pads, e.g., very thin pads or pads that use relatively
soft metals.
[0049] FIGS. 8A-B are microscope images of a preferred embodiment
of a blunt skate that has a rounded cross-section, similar to the
skate described in FIG. 2. FIG. 8A shows the skate prior to use and
FIG. 8B shows it after one million touch-down cycles. The skate has
a width of about 10 .mu.m and a length of 200 .mu.m. Note how the
skate is free of debris even after the one million touch-down
cycles. In fact, the debris has a tendency to be pushed off to the
sides of the skate and attach to non-critical portions of the probe
tip.
[0050] The probe card requires appropriate design and devices, such
as a source for delivering the test current i as well as
arrangements for providing the overdrive to apply the contact force
between the probes and the pads of the DUT. The design of probe
cards as well as the aforementioned devices are well-known to those
skilled in the art. It will be appreciated by those skilled
artisans that probes equipped with blunt skates in according to the
invention can be employed in probe cards of various designs,
including probe cards with and without space transformers. The
probes themselves can be removable in embodiments that use space
transformers or they can be permanently attached using soldering
techniques or mechanical locking such as press fit into a
conductive via.
[0051] The probes of invention are thus very versatile and are able
to establish reliable electrical contact with even densely spaced
fragile conductive pads or low-K pads. The pads can be arranged in
accordance with various geometries, including dense arrays. They
are able to do that because the combined scrub motion and
self-cleaning rotation of the blunt skate does not cause a high
stress concentration in the pad. Due to the large number of
possible variations and types of probes that employ blunt skates,
the scope of the invention should be judged by the appended claims
and their legal equivalents.
* * * * *